(Supported in part by NIH GMS23900 to R. Trimble) The function of an extrapallial fluid glycoprotein that is involved in the deposition of shell material in the mollusc Mytilus Edulis is being studied. The protein acts as a building block for the soluble organic matrix of the shell. Shell formation is an organic matrix mediated process which has parallels in the formation of bone and the mechanisms of bone disorders. A number of different specimen preparation procedures were tried in an attempt to make thin crystals, with the hope of determining the unit cell dimensions of the protein. Several samples were examined using the x-ray microanalysis system of the IVEM to measure sulfur content of protein, and to determine the relative amount of calcium in large and small crystal plates. The samples, however, were not ideal, so more work is needed. Dr. Hattan left Wadsworth center, so the work was suspended for the time being.